Nitro group hydrogenation

Most catalyst systems, if they show selectivity at all, favor preferential reduction of the less hindered 4-nitro group hydrogenation of 11 over Pt-on-C in acidic alcohol affords 10 in 70% yield (24). Similarly, Lazer et at. (61), selectively prepared 10 from 27 mmol II, 10 ml of 50% H2SO4, 60 ml HOAc, and 350 mg 5% Pt-on-C at 85 C and 30 psig. The hydrogenation is stopped at... 

Their favorable heat-transfer characteristics render micro reactors tools of interest for conducting nitro group hydrogenation via a gas/liquid process [17, 60]. 

If other active groups are y or 8 to the nitro group, hydrogenation can result in the formation of cyclic products. Esters condense with the product amine to give lactams. Ketones or aldehydes produce imines that can be hydrogenated further to an amine. The hydrogenation of y- or 5-nitro carboxylic acids under mild conditions, however, gives the amino acids in excellent yields.58.59 The... 

If other active groups are present y or S to the reducible nitro group, hydrogenation can result in formation of nitrogen heterocyclic products. Several such cyclizations provide an entry to indoles, such as reductive cyclizations of dinitrostyrene 1 [equation (a)], of o-nitrobenzyl ketone 2 [equation (b)], and of nitro nitrile 3 [equation (c)] , all of them carried out on palladium-on-carbon. 

---